Polymerization catalysts, organic transition metal compounds, process for preparing polyolefins and polyolefins

ABSTRACT

The present invention relates to catalyst systems for preparing isotactic polyolefins obtainable by reacting at least one chiral transition metal compound and at least one cocatalyst which is able to convert the chiral transition metal compound into a cation, where the chiral transition metal compound contains two bidentate chelating ligands connected to one another via a bridge and, if desired, one or two further monodentate ligands, with the four coordinating atoms of the two chelating ligands being in an approximately planar arrangement around the transition metal ion and up to two further ligands being located above and below this approximately planar coordination sphere formed by the four coordinating atoms of the two chelating ligands and, in the case of two such further ligands, these being in the trans position relative to one another, to the use of the catalyst systems of the present invention for preparing polyolefins, to a process for preparing polyolefins by polymerization or copolymerization of at least one olefin in the presence of one of the catalyst systems of the present invention, to the use of chiral transition metal compounds for preparing a catalyst system for the polymerization of olefins, to chiral transition metal compounds, to a process for preparing a catalyst system for olefin polymerization, to a process for preparing isotactic polyolefins, to polyolefins obtainable by a process according to the present invention, to polyolefin compositions comprising the polyolefins of the present invention and to products produced from such polyolefin compositions.

The present invention relates to catalyst systems for preparingisotactic polyolefins obtainable by reacting at least one chiraltransition metal compound and at least one cocatalyst which is able toconvert the chiral transition metal compound into a cation, where thechiral transition metal compound contains two bidentate chelatingligands connected to one another via a bridge and, if desired, one ortwo further monodentate ligands, with the four coordinating atoms of thetwo chelating ligands being in an approximately planar arrangementaround the transition metal ion and up to two further ligands beinglocated above and below this approximately planar coordination sphereformed by the four coordinating atoms of the two chelating ligands and,in the case of two such further ligands, these being in the transposition relative to one another.

In addition, the present invention provides for the use of the catalystsystems of the present invention for preparing polyolefins, provides aprocess for preparing polyolefins by polymerization or copolymerizationof at least one olefin in the presence of one of the catalyst systems ofthe present invention, provides for the use of chiral transition metalcompounds for preparing a catalyst system for the polymerization ofolefins, provides chiral transition metal compounds, provides a processfor preparing a catalyst system for olefin polymerization, provides aprocess for preparing isotactic polyolefins, provides polyolefinsobtainable by a process according to the present invention, providespolyolefin compositions comprising the polyolefins of the presentinvention and provides products produced from such polyolefincompositions.

Research and development on the use of organic transition metalcompounds, in particular metallocenes, as catalyst components for thepolymerization and copolymerization of olefins with the aim of preparingtailored polyolefins has been pursued intensively in universities and inindustry over the past 15 years.

Apart from metallocenes, new classes of transition metal compounds whichdo not contain any cyclopentadienyl ligands are now being examined to anincreasing extent as catalyst components.

Macromolecules 1997, 30, 171-175, disclosesethylenebis(salicylideniminato)zirconium dichloride and its use ascatalyst component in the polymerization of ethylene. The polymerizationof higher α-olefins such as propylene was not examined.

Adv. Synth. Catal. 2002, 344, No. 5, describes transition metalcomplexes of metals of group 4 of the Periodic Table of the Elementswith phenoxyimine ligands. In these complexes, the transition metal ionis surrounded by an octahedral arrangement of two phenoxyimine ligandsand two chloride ions, with the two oxygen atoms being in thetrans-position and the two nitrogen atoms and the two chlorine atomsbeing in the cis-position relative to one another. Polypropylenes havingdifferent tacticities depending on the cocatalyst and on thesubstitution pattern of the phenoxyimine ligands are described. While ahighly syndiotactic polypropylene is described, only atacticpolypropylene and an isotactic polypropylene having a low melting pointand a low isotacticity were obtained using the catalyst systemsdisclosed.

Chem. Commun., 2002, 352-353, describes transition metal complexesbearing, in each case, a biaryl-bridged bisphenoxyimine ligand and twochlorine ligands, their use in ethylene polymerization and possibledeactivation of the catalyst. The transition metal complexes of titaniumand zirconium which are described have a structure in which the metalion is octahedrally coordinated and the two oxygen atoms are in thetrans position and the two nitrogen atoms and the two chlorine atoms arein the Cis-position relative to one another.

WO 99/56699 lists various chiralbis(salicylidene)-1,2-diaminocyclohexane-transition metal complexes,some of which are commercially available. No olefin polymerizations aredescribed.

JP2002-179724 describes the polymerization of ethylene using a catalystsystem consisting ofN,N′-bis-(3,5-di-tert-butylsalicylidene)-1,2-diaminocyclohexanemanganese(III)chloride and methylaluminoxane (MAO). JP2002-179724 does not comment onthe geometry of the transition metal complex.

It is an object of the present invention to find catalyst systems basedon nonmetallocenes which make it possible to prepare highly isotacticpolyolefins, in particular isotactic polypropylenes having meltingpoints above 150° C. Furthermore, the catalyst systems should displaygood activities and be able to be used at industrially relevantpolymerization temperatures.

We have found that this object is achieved by the catalyst systemsmentioned at the outset.

The chiral transition metal compound contains a metal cation of anelement of group 3, 4, 5, 6, 7, 8, 9, 10, 11 or 12 of the Periodic Tableof the Elements or a lanthanide element, for example scandium, yttrium,titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium,molybdenum, tungsten, manganese, iron, cobalt, nickel, palladium, copperor zinc. Preference is given to a metal cation of an element of group 3,4, 5 or 6 of the Periodic Table of the Elements or a lanthanide element,in particular to a metal cation of an element of group 4 or 6 of thePeriodic Table of the Elements, for example titanium, zirconium, hafniumor chromium, preferably zirconium, hafnium or chromium.

The bridge in the chiral transition metal compound is preferably achiral bridge, in particular a bridge containing two chiralsp³-hybridized carbon atoms which are each joined directly to one of thetwo chelating ligands. Particular preference is given to a bridge inwhich the two chiral sp³-hybridized carbon atoms are joined directly toone another.

Each of the two bidentate chelating ligands preferably bears a singlenegative charge. The two coordinating atoms of the chelating ligandsare, for example, nitrogen, phosphorus, oxygen, sulfur, selenium ortellurium, in particular nitrogen, oxygen or sulfur. Preference is givento at least one, in particularly precisely one, of the two coordinatingatoms of the bidentate chelating ligand being a nitrogen atom.Particular preference is given to a bidentate chelating ligand havingone coordinating nitrogen atom and one coordinating oxygen atom.

A bidentate chelating ligand which forms a five-membered orsix-membered, in particular six-membered, metallacycle with the metalion is also preferred.

Preference is also given to bidentate chelating ligands which arebridged to one another via one of the two coordinating atoms, inparticular via a nitrogen atom.

Particular preference is given to bidentate chelating ligands having animine function derived from 1,3-dicarbonyl compounds, for exampleacetylacetone, benzoylacetone or 1,3-diphenyl-1,3-propanedione andsubstituted derivatives thereof, or derived from ortho-carbonylphenolderivatives, e.g. 2-hydroxybenzaldehyde or 2-hydroxyacetophenone orsubstituted derivatives thereof, with the imine function being formed byreaction of a carbonyl function with a primary amine. The monodentateligands are singly negatively charged anions, in particular halideanions, such as fluoride, chloride, bromide or iodide anions, inparticular chloride anions, hydride anions, C₁-C₄₀-hydrocarbon anions,such as methyl, tert-butyl, vinyl, phenyl or benzyl anions, alkoxy oraryloxy anions such as methoxy or phenoxy anions and amide anions suchas dimethylamide anions.

Particularly preferred monodentate ligands are chloride, methyl andbenzyl anions, in particular chloride anions.

The four coordinating atoms of the two bidentate chelating ligands arein an approximately planar arrangement around the transition metal ion.The transition metal ion does not need to lie exactly in the planeformed by the four coordinating atoms of the two bidentate chelatingligands. For the purposes of the present invention, approximately planarmeans that the four coordinating atoms of the two chelating ligands donot have to lay exactly in a plane, but the two coordinating atoms ofthe first chelating ligand can be slightly twisted relative to the twocoordinating atoms of the second chelating ligand. In the present case,an approximately planar arrangement of the four coordinating atoms ofthe two chelating ligands around the metal ion means that the anglebetween a first plane formed by the two coordinating atoms of the firstchelating ligand and the transition metal ion and a second plane formedby the two coordinating atoms of the second chelating ligand and thetransition metal ion is in the range from 0° to 20°, in particular inthe range from 0° to 10°.

Preference is given to catalyst systems as described above in which thechiral transition metal compound is a transition metal compound of theformula (I) or one of its enantiomers of the formula (I*)

where

M is an element of group 3, 4, 5, 6, 7, 8, 9, 10, 11 or 12 of thePeriodic Table of the Elements or the lanthanides,

Z may be identical or different and are each an organic or inorganicanionic ligand,

n1, n2 may be identical or different and are each 0 or 1, where n1+n2+2corresponds to the valence of M,

R¹ and R² may be identical or different and are each a C₁-C₄₀ radical,or R¹ and R²together with the atoms connecting them form a cyclic orpolycyclic ring system which may contain one or more, identical ordifferent heteroatoms selected from the group consisting of the elementsN, O, P, S and Si in place of carbon atoms in the ring system,

R³ is hydrogen or a C₁-C₄₀ radical, where R³ displays lower sterichindrance than R¹,

R⁴ is hydrogen or a C₁-C₄₀ radical, where R⁴ displays lower sterichindrance than R²,

R⁵ and R⁶ may be identical or different and are each hydrogen or aC₁-C₄₀ radical, or R¹ and R³, R² and R⁴, R¹ and R⁵ and/or R² and R⁶together with the atoms connecting them in each case form a cyclic orpolycyclic ring system which may contain one or more, identical ordifferent heteroatoms selected from the group consisting of the elementsN, O, P, S and Si in place of carbon atoms in the ring system,

X is a single bond between the two carbon atoms or is a divalent group,

Y¹, Y² may be identical or different and are each oxygen, sulfur,selenium, tellurium, an NR⁹ group or a PR⁹ group,

R⁷, R⁸, R⁹ may be identical or different and are each hydrogen,C₁-C₂₀-alkyl, C₂-C₂₀-alkenyl, C₆-C₂₂-aryl, alkylaryl or arylalkyl havingfrom 1 to 10 carbon atoms in the alkyl part and from 6 to 22 carbonatoms in the aryl part,

T¹, T², T⁴ and T⁴ may be identical or different and are each hydrogen ora C₁-C₄₀ radical, or T¹ and T³ and/or T² and T⁴ together with the carbonatoms connecting them in each case form a cyclic or polycyclic ringsystem which may contain one or more, identical or different heteroatomsselected from the group consisting of the elements N, O, P, S and Si inplace of carbon atoms in the ring system.

M¹ is an element of group 3, 4, 5, 6, 7, 8, 9, 10, 11 or 12 of thePeriodic Table of the Elements or the lanthanides, for example scandium,yttrium, titanium, zirconium, hafnium, vanadium, niobium, tantalum,chromium, molybdenum, tungsten, manganese, iron, cobalt, nickel,palladium, copper or zinc. Preference is given to a metal cation of anelement of group 3, 4, 5 or 6 of the Periodic Table of the Elements or alanthanide element, in particular to a metal cation of an element ofgroup 4 or 6 of the Periodic Table of the Elements, for exampletitanium, zirconium, hafnium or chromium, preferably zirconium, hafniumand chromium and particularly preferably zirconium.

The radicals Z can be identical or different, preferably identical, andare each an organic or inorganic anionic ligand. Z is preferablyhalogen, for example fluorine, chlorine, bromine or iodine, inparticular chlorine, hydrogen, C₁-C₂₀—, preferably C₁-C₄-alkyl, C₂-C₂₀—,preferably C₂-C₄-alkenyl, C₆-C₂₂—, preferably C₆-C₁₀-aryl, alkylaryl orarylalkyl having from 1 to 10, preferably from 1 to 4, carbon atoms inthe alkyl part and from 6 to 22, preferably from 6 to 10, carbon atomsin the aryl part, —OR⁷ or NR⁷R⁸. Z is particularly preferably chlorineor methyl.

n1, n2 may be identical or different and are each 0 or 1, with n1+n2+2corresponding to the valence of M. Preference is given to n1 and n2being identical and each equal to one for the elements of group 4 of thePeriodic Table of the Elements, so as to give an oxidation number of +4,and being identical and each equal to 0 for the elements of group 10 ofthe Periodic Table of the Elements, so as to give an oxidation number of+2.

R¹ and R² may be identical or different preferably identical, and areeach a C₁-C₄₀ radical such as a C₁-C₄₀-hydrocarbon radical orC₃-C₄₀—SiCR⁷)₃, or R¹ and R² together with the atoms connecting themform a cyclic or polycyclic ring system which may contain one or more,identical or different heteroatoms selected from the group consisting ofthe elements N, O, P, S and Si, preferably N, O and S, in particular N,in place of carbon atoms in the ring system. Preference is given to R¹and R² each being a cyclic, branched or unbranched C₁-C₂₀—, preferablyC₁-C₈-aryl radical, a C₂-C₂₀—, preferably C₂-C₈-alkenyl radical, aC₆-C₂₂, preferably C₆-C₁₀-aryl radical, an alkylaryl or arylalkylradical having from 1 to 10, preferably from 1 to 4, carbon atoms in thealkyl part and from 6 to 22, preferably from 6 to 10, carbon atoms inthe aryl part, with the radicals also being able to be halogenated, orC₃-C₁₈—, preferably C₃-C₈—Si(R⁷)₃, or R¹ and R³ together with the atomsconnecting them forming a cyclic 4- to 8-membered, preferably 5- or6-membered, ring system which may in turn bear C₁-C₂₀ radicals.Particular preference is given to R¹ and R² each being a cyclic,branched or unbranched C₁-C₈-alkyl radical, a C₈-C₁₀-aryl radical, analkylaryl or arylalkyl radical having from 1 to 4 carbon atoms in thealkyl part and from 6 to 10 carbon atoms in the aryl part ortrimethysilyl or R¹ and R² together with the atoms connecting themforming a cyclic 5- or 6-membered ring system which may in turn bearcyclic, branched or unbranched C₁-C₈-alkyl radicals, C₆-C₁₀-arylradicals, alkylaryl or arylalkyl radicals having from 1 to 4 carbonatoms in the alkyl part and from 6 to 10 carbon atoms in the aryl partor trimethylsilyl radicals. Examples of particularly preferred radicalsR¹ and R² are methyl, ethyl, n-propyl, isopropyl, n-butyl, i-butyl,s-butyl, t-butyl, n-pentyl, cyclopentyl, n-hexyl, cyclohexyl, n-heptyl,n-octyl, benzyl, 2-phenylethyl, phenyl, 2-tolyl, 3-tolyl, 4-tolyl,2,3-dimethylphenyl, 2,4-dimethylphenyl, 2,5-dimethylphenyl,2,6-dimethylphenyl, 3,4-dimethylphenyl, 3,5-dimethylphenyl,3,5-di(tert-butyl)phenyl, 2,4,6-trimethylphenyl, 2,3,4-trimethylphenyl,1-naphthyl, 2-naphthyl, phenanthryl, p-isopropylphenyl,p-tert-butylphenyl, p-s-butylphenyl, p-cyclohexylphenyl andp-trimethylsilylphenyl. Examples of particularly preferred ring systemsformed from the radicals R¹ and R² and the atoms connecting them are1,2-cyclohexylene, 1,2-cyclopentylene and 1-benzylpyrrolidin-3,4-ylene.

R³ is hydrogen or a C₁-C₄₀ radical such as a C₁-C₄₀ hydrocarbon radicalor C₃-C₄₀—Si(R⁷)₃, where R³ displays a lower steric hindrance than R¹.R³ is preferably hydrogen, a cyclic, branched or un-branched, inparticular unbranched, C₁-C₂₀—, preferably C₁-C₈-alkyl radical, aC₂-C₂₀—, preferably C₂-C₈-alkenyl radical, a C₈-C₂₂—, preferablyC₆-C₁₀-aryl radical, an alkylaryl or arylalkyl radical, preferably anarylalkyl radical, having from 1 to 10, preferably from 1 to 4, carbonatoms in the alkyl part and from 6 to 22, preferably from 6 to 10,carbon atoms in the aryl part, with the radicals also being able to behalogenated. Particular preference is given to R³ being hydrogen or anun-branched C₁-C₈-alkyl radical. R³ is very particularly preferablyhydrogen.

R⁴ is hydrogen or a C₁-C₄₀ radical such as a C₁-C₄₀-hydrocarbon radicalor C₃-C₄₀—Si(R⁷)₃, where R⁴ displays a lower steric hindrance than R².R⁴ is preferably hydrogen, a cyclic, branched or un-branched, inparticular unbranched, C₁-C₂₀—, preferably C₁-C₆-alkyl radical, aC₂-C₂₀—, preferably C₂-C₆-alkenyl radical, a C₆-C₂₂—, preferablyC₆-C₁₀-aryl radical, an alkylaryl or arylalkyl radical, preferably anarylalkyl radical, having from 1 to 10, preferably from 1 to 4, carbonatoms in the alkyl part and from 6 to 22, preferably from 6 to 10,carbon atoms in the aryl part, with the radicals also being able to behalogenated. Particular preference is given to R⁴ being hydrogen or anun-branched C₁-C₈-alkyl radical. R⁴ is very particularly preferablyhydrogen.

The steric hindrance displayed by a radical is determined by the spacewhich it occupies. For example, the steric hindrance increases in thefollowing order:

Hydrogen<methyl<ethyl<isopropyl<tert-butyl.

R⁵ and R⁶ may be identical or different, in particular identical, andare each hydrogen or a C₁-C₄₀ radical. R⁶ and R⁶ are preferablyhydrogen, a cyclic, branched or unbranched C₁-C₂₀—, preferablyC₁-C₈-alkyl radical, a C₂-C₂₀—, preferably C₂-C₈-alkenyl radical, aC₆-C₂₂—, preferably C₆-C₁₀-aryl radical, an alkylaryl or arylalkylradical having from 1 to 10, preferably from 1 to 4, carbon atoms in thearyl part, and from 6 to 22, preferably from 6 to 10, carbon atoms inthe aryl part, with the radicals also being able to be halogenated.Particular preference is given to R⁵ and R⁶ each being hydrogen, acyclic, branched or unbranched C₁-C₈-alkyl radical, a C₆-C₁₀-arylradical, an alkylaryl or arylalkyl radical having from 1 to 4 carbonatoms in the alkyl part and from 6 to 10 carbon atoms in the aryl part.Examples of particularly preferred radicals R⁵ and R⁶ are hydrogen,methyl, ethyl, n-propyl, isopropyl n-butyl, i-butyl, s-butyl, t-butyl,n-pentyl, cyclopentyl, n-hexyl, cyclohexyl, n-heptyl, n-octyl, benzyl,2-phenylethyl, phenyl, pentafluorophenyl, 2-tolyl, 3-tolyl, 4-tolyl,2,3-dimethylphenyl, 2,4-dimethylphenyl, 2,5-dimethylphenyl,2,6-dimethylphenyl, 3,4-dimethylphenyl, 3,5-dimethylphenyl,3,5-di(tert-butyl)phenyl, 2,4,6-trimethylphenyl, 2,3,4trimethylphenyl,1-naphthyl, 2-naphthyl, phenanthryl, p-isopropylphenyl,p-tert-butylphenyl, p-s-butylphenyl, p-cyclohexylphenyl andp-trimethylsilylphenyl, in particular hydrogen.

Furthermore, it is also possible for in each case two radicals R¹ andR³, R² and R⁴, R¹ and R⁵ and/or R² and R⁶ together with the atomsconnecting them to form a cyclic or polycyclic ring system which maycontain one or more, identical or different heteroatoms selected fromthe group consisting of the elements N, O, P, S and Si, in particular N,O and S, in place of carbon atoms in the ring system.

X is a single bond between the two carbon atoms or is a divalent group.Examples of divalent groups X are CR⁷R⁸, in particular CH₂, CR⁷R⁸—CR⁸R⁸,in particular CH₂—CH₂, (CR⁷R⁸)₃, (CR⁷R⁸)₄ or (CR⁷R⁸)₅. X is preferably asingle bond or CH₂, in particular a single bond.

Y¹ and Y² may be identical or different, in particular identical, andare each oxygen, sulfur, selenium, tellurium, an NR⁹ group or a PR⁹group, in particular oxygen.

R⁷, R⁸ and R⁹ may be identical or different and are each hydrogen,C₁-C₂, preferably C₁-C₄-alkyl, C₂-C₂₀—, preferably C₂-C₄-alkenyl,C₆-C₂₂—, preferably C₆-C₁₀-aryl, alkylaryl or arylalkyl having from 1 to10, preferably from 1 to 4, carbon atoms in the alkyl part and from 6 to22, preferably from 6 to 10, carbon atoms in the aryl part.

T¹, T², T³ and T⁴ may be identical or different and are each hydrogen ora C₁-C₄₀ radical, or T¹ and T³ and/or T² and T⁴ together with the carbonatoms connecting them in each case form a cyclic or polycyclic ringsystem which may contain one or more, identical or different heteroatomsselected from the group consisting of the elements N, O, P, S and Si inplace of carbon atoms in the ring system. Preference is given to T¹, T²,T³ and T⁴ each being a cyclic, branched or unbranched C₁-C₂₀—,preferably C₁-C₈-alkyl radical, a C₂-C₂₀—, preferably C₂-C₈-alkenylradical, a C₆-C₂₂—, preferably C₆-C₁₀-aryl radical, an alkylaryl orarylalkyl radical having from 1 to 10, preferably from 1 to 4, carbonatoms in the alkyl part and from 6 to 22, preferably from 6 to 10,carbon atoms in the aryl part, with the radicals also being able to behalogenated, or T¹ and T³ and/or T² and T⁴ together with the carbonatoms connecting them in each case forming substituted or unsubstituted,aromatic or partially hydrogenated 5 to 8-membered, in particular 5- or6-membered, ring systems which may contain heteroatoms selected from thegroup consisting of O, S and N and may in turn be part of largerpolycyclic ring systems. Particular preference is given to T¹ and T³ andT² and T⁴ together with the two connecting carbon atoms formingsubstituted or unsubstituted phenyl rings, thiophene rings or pyrrolerings, in particular phenyl rings, which may in turn be part of largerpolycyclic ring systems.

The radicals R¹, R², R³, R⁴, R⁶, R⁷, R⁸, R⁹, T¹, T², and T⁴ may,according to the present invention, also contain functional groupswithout altering the polymerization properties of the catalyst system ofthe present invention as long as these functional groups are chemicallyinert under the polymerization conditions.

Furthermore, the substituents are, for the purposes of the presentinvention, defined as follows unless restricted further

The term “C₁-C₄₀ radical” as used in the present text refers toC₁-C₄₀-alkyl radicals, C₁-C₁₀-fluoroalkyl radicals, C₁-C₁₂-alkoxyradicals, saturated C₃-C₂₀-heterocyclic radicals, C₆-C₄₀-aryl radicals.C₂-C₄₀-heteroaromatic radicals, C₆-C₁₀-fluoroaryl radicals,C₆-C₁₀-aryloxy radicals, C₃-C₁₈-trialkylsilyl radicals, C₂-C₂₀-alkenylradicals, C₂-C₂₀-alkynyl radicals, C₇-C₄₀-alkyl radicals orC₈-C₄₀-arylalkenyl radicals.

The term “alkyl” as used in the present text encompasses linear orsingly or multiply branched saturated hydrocarbons which may also becyclic. Preference is given to C₁-C₁₆-alkyl, such as methyl, ethyl,n-propyl, n-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl,n-decyl, cyclopentyl or cyclohexyl, isopropyl, isobutyl, isopentyl,isohexyl, sec-butyl or tert-butyl.

The term “alkenyl” as used in the present text encompasses linear orsingly or multiplicably branched hydrocarbons having one or more C—Cdouble bonds which may be cumulated or alternating.

The term “saturated heterocyclic radical” as used in the present textrefers to monocyclic or polycyclic, substituted or unsubstitutedhydrocarbon radicals in which one or more carbon atoms, CH groups and/orCH₂ groups are replaced by heteroatoms selected from the groupconsisting of O, S N and P. Preferred examples of substituted orunsubstituted saturated heterocyclic radicals are pyrrolidinyl,imidazolidinyl, pyrazolidinyl, piperidyl, piperazinyl, morpholinyl,tetrahydrofuranyl, tetrahydropyranyl, tetrahydrothienyl and the like,and also derivatives thereof which are substituted by methyl, ethyl,propyl, isopropyl and tert-butyl radicals.

The term “aryl” as used in the present text refers to aromatic and fusedor unfused polyaromatic hydrocarbon substituents which may beunsubstituted or monosubstituted or polysubstituted by linear orbranched C₁-C₁₈-alkyl, C₁-C₁₈-alkoxy, C₂-C₁₀-alkenyl orC₃-C₁₅-alkylalkenyl. Preferred examples of substituted and unsubstitutedaryl radicals are, in particular, phenyl, pentafluorophenyl,4-methylphenyl, 4-ethylphenyl, 4-propylphenyl, 4-isopropylphenyl,4-tert-butylphenyl, 4-methoxyphenyl, 1-naphthyl, 9-anthryl,9-phenanthryl, 3,5-dimethylphenyl, 3,5-di-tert-butylphenyl or4-trifluoromethylphenyl.

The term “heteroaromatic radical” as used in the present text refers toaromatic hydrocarbon substituents in which one or more carbon atoms arereplaced by nitrogen, phosphorus, oxygen or sulfur atoms or combinationsthereof. These can, like the aryl radicals, be unsubstituted ormono-substituted or polysubstituted by linear or branched C₁-C₁₈-alkyl,C₂-C₁₀-alkenyl or C₃-C₁₅-alkylalkenyl. Preferred examples are furyl,thienyl, pyrrolyl, pyridyl, pyrazolyl, imidazolyl, oxazolyl, thiazolyl,pyrimidinyl, pyrazinyl and the like, and also derivatives thereof whichare substituted by methyl, ethyl, propyl, isopropyl and tert-butylradicals.

The term “alkylalkenyl” as used in the present text encompasses linearor singly or multiplicably branched hydrocarbons having one or more C—Cdouble bonds which are isolated so that the substituent has both alkyland alkenyl sections.

The term “arylalkyl” as used in the present text refers toaryl-containing substituents whose aryl radical is linked via an alkylchain to the remainder of the molecule. Preferred examples are benzyl,substituted benzyl, phenethyl, substituted phenethyl, and the like.

The terms fluoroalkyl and fluoroaryl mean that at least one hydrogenatom, preferably more than one hydrogen atoms up to a maximum of allhydrogen atoms, of the respective substituent has/have been replaced byfluorine atoms. Examples of fluorine-containing substituents which arepreferred according to the present invention are trifluoromethyl,2,2,2-trifluoroethyl, pentafluorophenyl, 4trifluoromethylphenyl,4-perfluoro-tert-butylphenyl and the like.

Particular preference is given to catalyst systems as described above inwhich the chiral transition metal compound of the formula (I) or (I*) isa transition metal compound of the formula (Ia) or one its enantiomersof the formula (Ia*),

where

M is an element of group 4 or 6 of the Periodic Table of the Elements,

Z may be identical or different and are each halogen, hydrogen,C₁-C₁₀-alkyl, C₈-C₁₄-aryl, alkylaryl or arylalkyl having from 1 to 4carbon atoms in the alkyl part and from 6 to 10 carbon atoms in the arylpart,

n1, n2 may be identical or different and are each 0 or 1, with n1+n2+2corresponding to the valence of M,

R¹ and R² may be identical or different and are each a C₁-C₄₀ radical,or R¹ and R² together with the atoms connecting them form a cyclic orpolycyclic ring system which may contain one or more, identical ordifferent heteroatoms selected from the group consisting of the elementsN, O, P, S and Si in place of carbon atoms in the ring system.

R⁵ and R⁶ are identical and are each hydrogen or a C₁-C₄₀ radical,

R¹⁰, R¹¹, R¹² and R¹³ may be identical or different and are eachhydrogen or a C₁-C₄₀ radical, or two adjacent radicals R¹⁰, R¹¹, R¹² andR¹³ together with the two connecting carbon atoms may form a cyclic ringsystem.

M¹ is a element of group 4 or 6 of the Periodic Table of the Elements,for example titanium, zirconium hafnium, chromium, molybdenum ortungsten, preferably titanium, zirconium, hafnium or chromium,particularly preferably zirconium or hafnium, and very particularlypreferably zirconium.

The radicals Z may be identical or different, preferably identical, andare each halogen, for example fluorine, chlorine, bromine or iodine, inparticular chlorine, hydrogen, C₁-C₁₀—, preferably C₁-C₄-alkyl, C₆-C₁₄—,preferably C₆-C₁₀-aryl or alkylaryl or arylalkyl having from 1 to 4carbon atoms in the alkyl part and from 6 to 10, preferably 6, carbonatoms in the aryl part. Z is preferably chlorine, benzyl or methyl, inparticular chlorine.

The radicals R¹ and R² may be identical or different, in particularidentical, and are each a C₁-C₄₀ radical such as a C₁-C₄₀-hydrocarbonradical or C₃-C₄₀—Si(R⁷)₃, or R¹ and R² together with the atomsconnecting them form a cyclic or polycyclic, in particular monocyclicring system which may contain one or more, identical or differentheteroatoms selected from the group consisting of the elements N, O, P,S and Si, preferably N, O and S, in particular N, in place of carbonatoms in the ring system. Preference is given to R¹ and R² each being acyclic, branched or unbranched C₁-C₂₀—, preferably C₁-C₈-alkyl radical,a C₂-C₂₀—, preferably C₂-C₈-alkenyl radical, a C₈-C₂₂—, preferablyC₆-C₁₀-aryl radical, an alkylaryl or arylalkyl radical having from 1 to10, preferably from 1 to 4, carbon atoms in the alkyl part and from 6 to22, preferably from 6 to 10, carbon atoms in the aryl part, with theradicals also being able to be halogenated, or C₃-C₁₈—, preferablyC₂-C₆—Si(R⁷)₃, or R¹ and R² together with the atoms connecting themforming a cyclic 4- to 8-membered, preferably 5- or 6-membered, ringsystem which may in turn bear C₁-C₂₀ radicals. Particular preference isgiven to R¹ and R² each being a cyclic, branched or unbranchedC₁-C₈-alkyl radical, a C₈-C₁₀-aryl radical, an alkylaryl or arylalkylradical having from 1 to 4 carbon atoms in the alkyl part and tom 6 to10 carbon atoms in the aryl part or trimethylsilyl or R¹ and R² togetherwith the atoms connecting them forming a cyclic 5- or 6-membered ringsystem which may in turn bear cyclic, branched or unbranched C₁-C₈-alkylradicals, C₆-C₁₀-aryl radicals, alkylaryl or arylalkyl radicals havingfrom 1 to 4 carbon atoms in the alkyl part and from 6 to 10 carbon atomsin the aryl part or trimethylsilyl radicals. Examples of particularlypreferred radicals R¹ and R² are methyl, ethyl, n-propyl, isopropyl,n-butyl, i-butyl, s-butyl, t-butyl, n-pentyl, cyclopentyl, n-hexyl,cyclohexyl, n-heptyl, n-octyl, benzyl, 2-phenylethyl, phenyl, 2-tolyl,3-tolyl, 4-tolyl, 2,3-dimethylphenyl, 2,4-dimethylphenyl,2,5-dimethylphenyl, 2,6-dimethylphenyl, 3,4-dimethylphenyl,3,5-dimethylphenyl, 3,5-di(tert-butyl)phenyl, 2,4,6-trimethylphenyl,2,3,4-trimethylphenyl, 1-naphthyl, 2-naphthyl, phenanthryl,p-isopropylphenyl, p-tert-butylphenyl, p-s-butylphenyl,p-cyclohexylphenyl and p-trimethylsilylphenyl. Examples of particularlypreferred ring systems formed from the radicals R¹, R² and the atomsconnecting them are 1,2-cyclohexylene, 1,2-cyclopentylene and1-benzylpyrrolidin-3,4-ylene.

The radicals R⁵ and R⁸ are identical and are each hydrogen or a C₁-C₄₀radical. R⁵ and R⁶ are preferably each hydrogen, a cyclic, branched orunbranched C₁-C₂₀—, preferably C₁-C₆-alkyl radical, a C₆-C₂₂—,preferably C₆-C₁₀-aryl radical, an alkylaryl or arylalkyl radical havingfrom 1 to 10, preferably from 1 to 4, carbon atoms in the alkyl part,and from 6 to 22, preferably from 6 to 10, carbon atoms in the arylpart, with the radicals also being able to be halogenated. Particularpreference is given to R⁵ and R⁶ each being hydrogen, a cyclic, branchedor unbranched C₁-C₈-alkyl radical, a C₆-C₁₀-aryl radical, an alkylarylor arylalkyl radical having from 1 to 4 carbon atoms in the alkyl partand from 6 to 10 carbon atoms in the aryl part. Examples of particularlypreferred radicals R⁵ and R⁶ are hydrogen, methyl, ethyl, n-propyl,isopropyl, n-butyl, i-butyl, s-butyl, t-butyl, n-pentyl, cyclopentyl,n-hexyl, cyclohexyl, n-heptyl, n-octyl, benzyl, 2-phenylethyl, phenyl,pentafluorophenyl, 2-tolyl, 3-tolyl, 4-tolyl, 2,3-dimethylphenyl,2,4-dimethylphenyl, 2,5-dimethylphenyl, 2,6-dimethylphenyl,3,4-dimethylphenyl, 3,5-dimethylphenyl, 3,5-di(tert-butyl)phenyl,2,4,6-trimethylphenyl, 2,3,4-trimethylphenyl, 1-naphthyl, 2-naphthyl,phenanthryl, p-isopropylphenyl, p-tert-butylphenyl, p-s-butylphenyl,p-cyclohexylphenyl and p-trimethylsilylphenyl, in particular methyl,phenyl or hydrogen, especially hydrogen.

The radicals R⁷ may be identical or different and are each C₁-C₄-alkylsuch as methyl, ethyl or tert-butyl, in particular methyl, C₆-C₁₀-arylsuch as phenyl or naphthyl, in particular phenyl, alkylaryl or arylalkylhaving from 1 to 4 carbon atoms in the alkyl part and from 6 to 10,preferably 6. carbon atoms in the aryl part.

The radicals R¹⁰, R¹¹, R¹² and R¹³ may be identical or different and areeach hydrogen or a C₁-C₄₀ radical, for example a C₁-C₄₀-hydrocarbonradical, or C₃-C₄₀—Si(R⁷)₃, or two adjacent radicals R¹⁰, R¹¹, R¹² andR¹³ together with the two carbon atoms connecting them can form a cyclicring system which may contain one or more, identical or differentheteroatoms selected from the group consisting of the elements N, O, P,S and Si, preferably N, O or S, in place of carbon atoms. Preference isgiven to the radicals R¹⁰, R¹¹, R¹² and R¹³ each being hydrogen, acyclic, branched or unbranched C₁-C₂₀, preferably C₁-C₈-alkyl radical, aC₈-C₂₂—, preferably C₆-C₁₀-aryl radical, an alkylaryl or arylalkylradical having from 1 to 10, preferably from 1 to 4, carbon atoms in thealkyl part and 6 to 22, preferably from 6 to 10, carbon atoms in thearyl part, with the radicals also being able to be halogenated, orC₃-C₁₈—, preferably C₃-C₈—Si(R⁷)₃, or two adjacent radicals R¹⁰, R¹¹,R¹² and R¹³ together with the two carbon atoms connecting them forming acyclic 4- to 8-membered, preferably 5- or 6-membered, in particular6-membered, ring system which may in turn bear C₁-C₂₀ radicals.Particular preference is given to the radicals R¹⁰, R¹¹, R¹² and R¹³being hydrogen, a cyclic, branched or unbranched C₁-C₈-alkyl radical, aC₆-C₁₀-aryl radical, an alkylaryl or arylalkyl radical having from 1 to4 carbon atoms in the alkyl part and from 6 to 10 carbon atoms in thearyl part or trimethylsilyl or two adjacent radicals R¹⁰, R¹¹, R¹² andR¹³ together with the two carbon atoms connecting them forming a cyclic5 or 6-membered ring system which may in turn bear cyclic, branched orun-branched C₁-C₈-alkyl radicals, C₈-C₁₀-aryl radicals, alkylaryl orarylalkyl radicals having from 1 to 4 carbon atoms in the alkyl part andfrom 6 to 10 carbon atoms in the aryl part or trimethysilyl radicals.

Examples of particularly preferred radicals R¹⁰, R¹¹, R¹² and R¹³ aremethyl, ethyl, n-propyl, isopropyl, n-butyl, 1-butyl, s-butyl, t-butyl,n-pentyl, cyclopentyl, n-hexyl, cyclohexyl, n-heptyl, n-octyl,adamantyl, benzyl, triphenylmethyl, 1-1-diphenylethyl,1-methyl-1-phenylethyl, 2-phenylethyl, phenyl, pentafluorophenyl,2-tolyl, 3-tolyl, 4-tolyl, 2,3-dimethylphenyl, 2,4-dimethylphenyl,2,5-dimethylphenyl, 2,6-dimethylphenyl, 3,4-dimethylphenyl,3,5-dimethylphenyl, 3,5-di(tert-butyl)phenyl, 2,4,6-trimethylphenyl,2,3,4-trimethylphenyl, 1-naphthyl, 2-naphthyl, phenanthryl,p-isopropylphenyl, p-tert-butylphenyl, p-s-butylphenyl,t-cyclohexylphenyl and p-trimethylsilylphenyl. Examples of particularlypreferred ring systems formed from two adjacent radicals R¹⁰, R¹¹, R¹²and R¹³ together with the two carbon atoms connecting them are a phenylring, pyrridine ring or thiophene ring.

It is preferred that radicals R¹⁰, R¹¹, R¹² and R¹³ having the sameindices are in each case identical.

It is preferred that the radical R¹⁰ is not hydrogen and is a bulkyradical such as a branched or cyclic C₁-C₁₀-alkyl radical, a C₆-C₁₀-arylradical, an alkylaryl or arylalkyl radical having from 1 to 4 carbonatoms in the alkyl part and from 6 to 10 carbon atoms in the aryl part.Examples of particularly preferred radicals R¹⁰are isopropyl, t-butyl,cyclohexyl, adamantyl, triphenylmethyl, 1,1-diphenylethyl,1-methyl-1-phenylethyl, phenyl, pentafluorophenyl,3,5-di(tert-butyl)phenyl, 2,4,6-trimethylphenyl, 1-naphthyl,phenanthryl, p-tert-butylphenyl. An example of a particularly preferredring system formed from the radicals R¹⁰ and R¹¹ together with the twocarbon atoms connecting them is a phenyl ring.

Illustrative examples of transition metal compounds which can be used asconstituent of the catalyst systems of the present invention are,without implying any restriction of the scope of the invention:

The preparation of the bridged chelating ligands and the chiraltransition metal compounds prepared therefrom is known in principle fromthe literature and is described, for example, in WO 99/56699.

The cocatalyst which together with the chiral transition metal compounddescribed in more detail above forms the novel, polymerization-activecatalyst system is able to convert the chiral transition metal compoundinto a cation.

Suitable cation-forming compounds are, for example, aluminoxanes, stronguncharged Lewis acids, ionic compounds having a Lewis-acid cation ortonic compounds containing a Brönsted acid as cation. Preference isgiven to an aluminoxane as cocatalyst.

As aluminoxanes, it is possible, for example, to use the compoundsdescribed in WO 00131 090. Particularly useful compounds of this typeare open-chain or cyclic aluminoxane compounds of the formula (II) or(III)

where

R¹⁴ is a C₁-C₄-alkyl group, preferably a methyl or ethyl group, and m isan integer from 5 to 30, preferably from 1a to 25.

These oligomeric aluminoxane compounds are usually prepared by reactinga solution of trialkylaluminum with water. In general, the oligomericaluminoxane compounds obtained in this way are in the form of mixturesof both linear and cyclic chain molecules of various lengths, so that mis to be regarded as a mean. The aluminoxane compounds can also bepresent in admixture with other metal alkyls, preferably aluminumalkyls.

Furthermore, it is also possible to use modified aluminoxanes in whichsome of the hydrocarbon radicals or hydrogen atoms have been replaced byalkoxy, aryloxy, siloxy or amide radicals in place of the aluminoxanecompounds of the formula (II) or (III).

It has been found to be advantageous to use the chiral transition metalcompound and the aluminoxane compounds in such amounts that the atomicratio of aluminum from the aluminoxane compounds to the transition metalfrom the transition metal compound is in the range from 10:1 to 1000:1,preferably in the range from 20:1 to 500:1 and in particular in therange from 30:1 to 400:1.

As strong, uncharged Lewis acids, preference is given to compounds ofthe formula (IV)M²X¹X²X³   (IV)

where

M² is an element of group 13 of the Periodic Table of the Elements, inparticular B, Al or Ga, preferably B.

X¹, X² and X³ are each, independently of one another, hydrogen,C₁-C₁₀-alkyl, C₆-C₁₅-aryl, alkylaryl, arylalkyl, haloalkyl or haloaryleach having from 1 to 10 carbon atoms in the alkyl radical and from 6 to20 carbon atoms in the aryl radical or fluorine, chlorine, bromine oriodine, in particular haloaryl, preferably pentafluorophenyl.

Further examples of strong, uncharged Lewis acids are mentioned in WO00/31090.

Particular preference is given to compounds of the formula (IV) in whichX¹, X² and X³ are identical, preferably tris(pentafluorophenyl)borane.

Strong uncharged Lewis acids which are suitable as cation-formingcompounds also include the reaction products of the reaction of aboronic acid with two equivalents of a trialkyl aluminum or the reactionproducts of the reaction of a trialkyl aluminum with two equivalents ofan acidic fluorinated, in particular perfluorinated, carbon compoundsuch as pentafluorophenol or bis(pentafluorophenyl)borinic acid.

Suitable ionic compounds having Lewis-acid cations include salt-likecompounds of the cation of the formula (V)[(Y^(a+))Q₁Q₂ . . . Q_(z)]^(d+)  (V)

where

Y is an element of groups 1 to 16 of the Periodic Table of the Elements,

Q₁ to Q_(z) are singly negatively charged groups such as C₁-C₂₈-alkyl,C₆-C₁₅-aryl, alkylaryl, arylalkyl, haloalkyl, haloaryl each having from5 to 20 carbon atoms in the aryl radical and from 1 to 28 carbon atomsin the alkyl radical, C₃-C₁₀-cycloalkyl, which may bear C₁-C₁₀-alkylgroups as substituents, halogen, C₁-C₂₈-alkoxy, C₆-C₁₅-aryloxy, silyl ormercaptyl groups,

a is an integer from 1 to 6 and

z is an integer from 0 to 5, and

d corresponds to the difference a−z, but d is greater than or equal to1.

Particularly useful cations are carbonium cations, oxonium cations andsulfonium cations and also cationic transition metal complexes.Particular mention may be made of the triphenylmethyl cation, the silvercation and the 1,1′-dimethylferrocenyl cation. They preferably havenon-coordinating counterions, in particular borane compounds as arementioned in WO 91/09882, preferably tetrakis(pentafluorophenyl)borate.

Salts having non-coordinating anions can also be prepared by combining aborane or aluminum compound, e.g. an aluminum alkyl, with a secondcompound which can react to link two or more borane or aluminum atoms,e.g. water, and a third compound which forms an ionizing ionic compoundwith the borane or aluminum compound, e.g. triphenylchloromethane. Afourth compound which likewise reacts with the borane or aluminumcompound. e.g. pentafluorophenol, can additionally be added.

Ionic compounds containing Brönsted acids as cations preferably likewisehave non-coordinating counterions. As Brönsted acids, particularpreference is given to protonated amine or aniline derivatives.Preferred cations are N,N-demethylanilinium,N,N-diemethylcyclohexylammonium and N,N-dimethylbenzylammonium and alsoderivatives of the latter two.

Preferred ionic compounds as cation-forming compounds are, inparticular, N,N-dimethylanilinium tetrakis(pentafluorophenyl)borate,N,N-dimethylcyclohexylammonium tetrakis(pentafluorophenyl)borate andN,N-dimethylbenzylammonium tetrakis(pentafluorophenyl)borate.

It is also possible for two or more borate anions to be joined to oneanother, as in the dianion [(C₈F₅)₂B—C₆F₄—B(C₆F₅)₂]²⁻, or the borateanion can be bound via a bridge having a suitable functional group tothe surface of a support particle.

Further suitable cation-forming compounds are listed in WO 00131090.

The amount of strong, uncharged Lewis acids, ionic compounds havingLewis-acid cations or ionic compounds containing Brönsted acids ascations is usually from 0.1 to 20 equivalents, preferably from 1 to 10equivalents, based on the chiral transition metal compound.

Suitable cation-forming compounds also include borane-aluminum compoundssuch as di[bis(pentafluorophenyl)boroxy]methylalene. Appropriateborane-aluminum compounds are disclosed, for example, in WO 99106414.

It is also possible to use mixtures of all the abovementionedcation-forming compounds. Preferred mixtures comprise aluminoxanes, inparticular methylaluminoxane, and an ionic compound, in particular onecontaining the tetrakis(pentafluorophenyl)borate anion, and/or a stronguncharged Lewis acid, in particular tris(pentafluorophenyl)borane.

Preference is given to using both the transition metal compound and thecation-forming compounds in a solvent, preferably an aromatichydrocarbon having from 6 to 20 carbon atoms, in particular xylenes andtoluene.

The catalyst system of the present invention can further comprise ametal compound of the formula (VI),M³(R¹⁵)_(r)(R¹⁶)_(s)(R¹⁷)_(t)   (VI)

where

M³ is an alkali metal, an alkaline earth metal or a metal of group 13 ofthe Periodic Table of the Elements, i.e. borane, aluminum, gallium,indium or thallium,

R¹⁵ is hydrogen, C₁-C₁₀-alkyl, C₅-C₁₅-aryl, alkylaryl or arylalkyl eachhaving from 1 to 10 carbon atoms in the alkyl part and from 6 to 20carbon atoms in the aryl part,

R¹⁶ and R¹⁷ are identical or different and are each hydrogen, halogen,C₁-C₁₀-alkyl, C₅-C₁₅-aryl, alkylaryl, arylalkyl or alkoxy each havingfrom 1 to 10 carbon atoms in the alkyl radical and from 6 to 20 carbonatoms in the aryl radical,

r is an integer from 1 to 3,

and

s and t are integers from 0 to 2, with the sum r+s+t corresponding tothe valence of M³, where the metal compound of the formula (VI) isusually not identical to the cation-forming compound. It is alsopossible to use mixtures of various metal compounds of the formula (VI).

Among the metal compounds of the formula (VI), preference is given tothose in which

M³ is lithium, magnesium or aluminum and

R¹⁶ and R¹⁷ are each C₁-C₁₀-alkyl.

Particularly preferred metal compounds of the formula (VI) aren-butyllithium, n-butyl-n-octylmagnesium, n-butyl-n-heptylmagnesium,tri-n-hexylaluminum, triisobutylaluminum, triethylaluminum andtrimethylaluminum and mixtures thereof.

If a metal compound of the formula (VI) is used, it is preferablypresent in the catalyst system of the present invention in such anamount that the molar ratio of M³ from formula (VI) to transition metalfrom the chiral transition metal compound is from 800:1 to 1:1, inparticular from 200:1 to 2:1.

The catalyst system of the present invention particularly preferablyfurther comprises a support.

To obtain such a supported catalyst system, the unsupported catalystsystem can be reacted with a support. In principle, the support, thechiral transition metal compound and the cocatalyst can be combined inany order. The chiral transition metal compound and the cocatalyst canbe immobilized independently of one another or simultaneously. Aftereach individual process step, the solid can be washed with suitablyinert solvents, e.g. aliphatic or aromatic hydrocarbons.

Supports used are preferably finely divided supports which can be anyorganic or inorganic, inert solid. In particular, the support is aporous solid such as talc, a sheet silicate, an inorganic oxide or afinely divided polymer powder (e.g. polyolefin).

Suitable inorganic oxides may be found among oxides of elements ofgroups 2, 3, 4, 6, 13, 14, 15 and 16 of the Periodic Table of theElements. Examples of oxides preferred as supports include siliconedioxide, aluminum oxide and mixed oxides of the elements calcium,aluminum, silicone, magnesium or titanium and corresponding oxidemixtures. Other inorganic oxides which can be used alone or incombination with the abovementioned preferred oxidic supports are, forexample, MgO, ZrO₂, TiO₂ or B₂O₃. An example of a preferred mixed oxideis calcite hydrotalcite.

The support materials used preferably have a specific surface area inthe range from 10 to 1000 m²/g, a pore volume in the range from 0.1 to 5ml/g and a mean particle size of from 1 to 500 μm.

Preference is given to supports having a specific surface area in therange from 50 to 600 m²/g, a pore volume in the range from 0.5 to 3.5ml/g and a mean particle size in the range from 5 to 350 μm. Particularpreference is given to supports having a specific surface area in therange from 200 to 400 m²/g, a pore volume in the range from 0.8 to 3.0ml/g and a mean particle size of from 10to100 μm.

The inorganic support can be subjected to a thermal treatment, e.g. toremove adsorbed water. Such a drying treatment is generally carried outat from 80 to 300° C., preferably from 100 to 200° C., with drying atfrom 100 to 200° C. preferably being carried out under reduced pressureand/or under a blanket of inert gas (e.g. nitrogen), or the inorganicsupport can be calcined at from 200 to 1000° C. to obtain, ifappropriate, the desired structure of the solid and/or to set thedesired OH concentration on the surface. The support can also be treatedchemically using customary desiccants such as metal alkyls, preferablyaluminum alkyls, chlorosilanes or SiCl₄, or else methylaluminoxane.Appropriate treatment methods are described, for example, in WO00/31090. The inorganic support material can also be chemicallymodified. For example, treatment of silica gel with (NH₄)_(s)SiF₅ leadsto fluorination of the silica gel surface or treatment of silica gelswith silanes containing nitrogen-, fluorine- or sulfur-containing groupsleads to correspondingly modified silica gel surfaces.

Organic support materials such as finely divided polyolefin powders(e.g. polyethylene, polypropylene or polystyrene) can also be used andare preferably likewise freed of adhering moisture, solvent residues orother impurities by appropriate purification and drying operationsbefore use. It is also possible to use functionalized polymer supports,e.g. ones based on polystyrenes, via whose functional groups, forexample ammonium or hydroxy groups, at least one of the catalystcomponents can be immobilized.

In a preferred embodiment of the preparation of the supported catalystsystem of the present invention, at least one chiral transition metalcompound is brought into contact with at least one cocatalyst ascation-forming compound in a suitable solvent, preferably giving asoluble reaction product, an adduct or a mixture.

The preparation obtained in this way is then mixed with the dehydratedor passivated support material, the solvent is removed and the resultingsupported transition metal compound catalyst system is dried to ensurethat all or most of the solvent is removed from the pores of the supportmaterial. The supported catalyst is obtained as a free-flowing powder.Examples of the industrial implementation of the above process aredescribed in WO 96100243, WO 98/40419 or WO 00/05277.

A further preferred embodiment comprises firstly applying thecation-forming compound to the support component and subsequentlybringing this supported cation-forming compound into contact with thechiral transition metal compound.

Combinations obtained by combining the following components aretherefore likewise of importance as cocatalyst systems:

1st component: at least one defined borane or aluminum compound,

2nd component: at least one uncharged compound which has at least oneacidic hydrogen atom,

3rd component at least one support, preferably an inorganic oxidicsupport, and optionally, as 4th component, a base, preferably an organicnitrogen-containing base, for example an amine, an aniline derivative ora nitrogen heterocycle.

The borane or aluminum compounds used in the preparation of thesupported cocatalysts are preferably compounds of the formula (VII)

where

R¹⁸ are identical or different and are each hydrogen, halogen,C₁-C₂₀-alkyl, C₁-C₂₀-haloalkyl, C₁-C₁₀-alkoxy, C₈-C₂₀-aryl,C₈-C₂₀-haloaryl, C₆-C₂-aryloxy, C₇-C₄₀-arylalkyl, C₇-C₄₀-haloarylalkyl,C₇-C₄₀-alkylaryl, C₇-C₄₀-haloalkylaryl or an OSiR¹⁹ ₃ group, where

R¹⁹ are identical or different and are each hydrogen, halogen,C₁-C₂₀-alkyl, C₁-C₂₀-haloalkyl, C₁-C₁₀-alkoxy, C₆-C₂₀-aryl,C₆-C₂₀-haloaryl, C₆-C₂₀-aryloxy, C₇-C₄₀-arylalkyl,

C₇-C₄₀-haloarylalkyl, C₇-C₄₀-alkylaryl, C₇-C₄₀-haloalkylaryl, preferablyhydrogen, C₁-C₈-alkyl or C₇-C₂₀-arylalkyl, and

M⁴ is borane or aluminum, preferably aluminum.

Particularly preferred compounds of the formula (VII) aretrimethylaluminum, trimethylaluminum and tri-isobutylaluminum.

The uncharged compounds which have at least one acidic hydrogen atom andcan react with compounds of the formula (VII) are preferably compoundsof the formulae (VII), (IX) and (X).R²⁰-D-H   (VIII)(R²⁰)_(3-h)—B—(D-H)_(h)   (IX)H-D-R²¹-D-H   (X)

where

R²⁰ are identical or different and are each hydrogen, halogen, aboron-free C₁-C₄₀ group such as C₁-C₂₀-alkyl, C₁-C₂₀-haloalky,C₁-C₁₀-alkoxy, C₈-C₂₀-aryl, C₆-C₂₀-haloaryl, C₆-C₂₀-aryloxy,C₇-C₄₀-arylalkyl, C₇-C₄₀-haloarylalkyl, C₇-C₄₀-alkylaryl,C₇-C₄₀-haloalkylaryl, an Si(R²²)₃ group or a CH(SiR²² _(s))₂ group,where is a boron-free C₁-C₄₀ group such as C₁-C₂₀-alkyl,C₁-C₂₀-haloalkyl, C₁-C₁₀-alkoxy, C₆-C₂₀-aryl, C₆-C₂₀-haloaryl,C₆-C₂₀-aryloxy, C₇-C₄₀-arylalkyl, C₇-C₄₀-haloarylalkyl;C₇-C₄₀-alkylaryl, C₇-C₄₀-haloalkylaryl, and

R²¹ is a divalent C₁-C₄₀ group such as C₁₀-C₂₀-alkylene,C₁-C₂₀-haloalkylene, C₅-C₂₀-arylene, C₆-C₂₀-haloarylene,C₇-C₄₀-arylalkylene, C₇-C₄₀-haloarylalkylene, C₇-C₄₀-alkylarylene,C₇-C₄₀-haloalkylarylene,

D is an element of group 16 of the Periodic Table of the Elements or anNR²³ group, where R²³ is hydrogen or a C₁-C₂₀-hydrocarbon radical suchas C₁l-C₂₀-alkyl or C₈-C₂₀-aryl, preferably oxygen, and

h is 1 or 2.

Suitable compounds of the formula (VIII) include water, alcohols, phenolderivatives, thiophenol derivatives or aniline derivatives, withhalogenated and in particular perfluorinated alcohols arid phenols beingof particular importance. Examples of particularly useful compounds arepentafluorophenol, 1,1-bis(pentafluorophenyl)methanol and4hydroxy-2,2′,3,3′,4,4′,5,5′,6,6′-nonafluorobiphenyl.

Suitable compounds of the formula (IX) include boronic acids and borinicacids; particular mention may be made of borinic acids havingperfluorinated aryl radicals, for example (C₆F₅)₂BOH. Suitable compoundsof the formula (X) include dihydroxy compounds in which the divalentcarbon-containing group is preferably halogenated and in particularperfluorinated. An example of such a compound is4,4′-dihydroxy-2,2′,3,3′,5,5′,6,6′-octafluorobiphenyl hydrate.

Examples of combinations of compounds of the formula (VII) withcompounds of the formula (VIII) or (X) aretrimethylaluminum/pentafluorophenol,trimethylaluminum/1-bis(pentafluorophenyl)methanol,trimethylaluminum/4-hydroxy-2,2′,3,3′,4′,5,5′,6,6′-nonafluorobiphenyl,triethylaluminum/pentafluorophenol,tri-isobutylaluminum/pentafluorophenol andtriethylaluminum/4,4′-dihydroxy2,2′,3,3′,5,5′,6,6′-octafluorobiphenylhydrate, with, for example, reaction products of the following typebeing able to be formed.

Examples of reaction products from the reaction of at least one compoundof the formula (VII) with at least one compound of the formula (IX) are:

The way in which the components are combined is in principle immaterial.

In one possible method, the reaction products of the reaction of atleast one compound of the formula (VII) with at least one compound ofthe formula (VIII), (IX) or (X) and optionally the organic nitrogen baseare combined with an organometallic compound of the formula (II), (III),(IV) and/or (VI) and then with the support to form the supportedcocatalyst system.

In a preferred variant, the 1st component, e.g. compounds of the formula(VII), and the 2nd component, e.g. compounds of the formula (VIII), (IX)or (X), and also a support as 3rd component and a base as 4th componentare combined separately and subsequently reacted with one another,preferably in an inert solvent or suspension medium. The supportedcocatalyst formed can then be freed of the inert solvent or suspensionmedium before being reacted with the chiral transition metal compoundused according to the present invention and, if appropriate, a metalcompound of the formula (VI) to give the catalyst system of the presentinvention.

Furthermore, it is also possible firstly to prepolymerize the catalystsolid according to the present invention with α-olefins, preferablylinear C₂-C₁₀-1-alkenes and in particular ethylene or propylene and thento use the resulting prepolymerized catalyst solid in the actualpolymerization. The molar ratio of catalyst solid used in theprepolymerization to monomer polymerized onto it is usually in the rangefrom 1:0.1 to 1:200.

Furthermore, a small amount of an olefin, preferably an α-olefin, forexample vinylcyclohexane, styrene or phenyldimethylvinylsilane, asmodifying component, an antistatic or a suitable inert compound such asa wax or an oil can be added as additive during or after the preparationof the supported catalyst system of the present invention. The molarratio of additives to chiral transition metal compound is in this caseusually from 1-1000 to 1000:1, preferably from 1:5 to 20:1.

The novel catalyst systems based on the above-described chiraltransition metal compounds give isotactic polyolefins, in particularisotactic polypropylene, having a higher melting point than do thepreviously known catalyst systems.

The invention further provides for the use of a novel catalyst system asdescribed above for preparing polyolefins and provides processes forpreparing polyolefins by polymerization or copolymerization of at leastone olefin, in particular propylene in the presence of a novel catalystsystem as described above.

In general, the catalyst system of the present invention is usedtogether with a further metal compound of the formula (VI), which may bedifferent from the metal compound or compounds of the formula (VI) usedin the preparation of the catalyst system of the present invention forthe polymerization or copolymerization of olefins. The further metalcompound is generally added to the monomer or to the suspension mediumand serves to free the monomer of substances which could adverselyaffect the catalyst activity. It is also possible to add one or morefurther cation-containing compounds to the catalyst system of thepresent invention during the polymerization process.

The olefins can be functionalized, olefinically unsaturated compoundssuch as ester or amide derivatives of acrylic or methacrylic acid, forexample acrylates, methacrylates or acrylonitrile, or can be nonpolarolefinic compounds, including aryl-substituted α-olefins.

Preference is given to polymerizing olefins of the formulaR^(m)—CH═CH—R^(n), where R^(m) and R^(n) are identical or different andare each hydrogen or a hydrocarbon radical having from 1 to 20 carbonatoms, in particular from 1 to 10 carbon atoms, or R^(m) and R^(n)together with the atoms connecting them can form one or more rings.

Examples of such olefins are 1-olefins having from 2 to 40, preferablyfrom 2 to 10, carbon atoms, for example ethylene, propylene, 1-butene,1-pentene, 1-hexene, 1-heptene, 1-octene, 1-decene or4-methyl-1-pentene, or unsubstituted or substituted vinylaromaticcompounds such as styrene and styrene derivatives, or dienes such as1,3-butadiene, 1,4-hexadiene, 1,7-octadiene, 5-ethylidene-2-norbornene,norbornadiene, ethylnorbornadiene or cyclic olefins such as norbornene,tetracyclododecene or methylnorbornene. Preference is given to,propylene, 1-butene, 1-hexene or 4-methyl-1-pentene, in particularpropylene.

The catalyst system of the present invention is particularly preferablyused for homopolymerizing propylene or ethylene, in particularpropylene, or copolymerizing ethylene with C₃-C₈-α-olefins such aspropylene, 1-butene, 1-pentene, 1-hexene and/or 1-octene and/or cyclicolefins such as norbornene and/or dienes having from 4 to 20 carbonatoms, e.g. 1,4-hexadiene, norbornadiene, ethylidenenorbornene orethylnorbornadiene, or very particularly preferably copolymerizingpropylene with ethylene and/or 1 -butene. Examples of such copolymersare propylenelethylene, propylene/1-butene, ethylene/1-butene,ethylene/1-hexene, ethylene/1-octene copolymers,ethylene/propylene/ethylidenenorbornene orethylene/propylene/1,4-hexadiene terpolymers.

The polymerization can be carried out in a known manner in bulk, insuspension, in the gas phase or in a supercritical medium in thecustomary reactors used for the polymerization of olefins. It can becarried out batchwise or preferably continuously in one or more stages.Solution processes, suspension processes, stirred gas-phase processes orgas-phase fluidized-bed processes are all possible. As solvent orsuspension medium, it is possible to use inert hydrocarbons, for exampleisobutane, or else the monomers themselves.

The polymerization can be carried out at from −60 to 300° C. atpressures in the range from 0.5 to 3000 bar. Preference is given totemperatures in the range from 50 to 200° C., in particular from 60 to100° C., and pressures in the range from 5 to 100 bar, in particularfrom 15 to 70 bar. The mean residence times are usually from 0.5 to 5hours, preferably from 0.5 to 3 hours. As molar mass regulator and/or toincrease the activity, hydrogen can be employed in the polymerization.It is also possible to use customary additives such as antistatics. Thecatalyst system of the present invention can be used directly for thepolymerization, i.e. it is added in pure form into the polymerizationsystem, or it is admixed with inert components such as paraffins, oilsor waxes to improve meterability.

The catalyst systems of the present invention are very particularlyuseful for preparing propylene homopolymers having high melting points.

The invention further provides for the use of a chiral transition metalcompound of the formula (Ib) or one of its enantiomers of the formula(Ib*) for preparing a catalyst system for the polymerization of olefins,in particular for homo- or copolymerization of propylene,

where the variables are as defined for the formulae (I) and (I*).

where the variables are as defined for the formulae (Ia) and (Ia*) isparticularly preferred for the preparation of a catalyst system.

The invention further provides chiral transition metal compounds of theformula (Ib) or (Ib*) in which M is zirconium or hafnium, in particularzirconium.

The invention additionally provides a process for preparing a catalystsystem for olefin polymerization, which comprises reacting at least onetransition metal compound of the formula (Ib) or (Ib*) with at least onecation-forming compound, and also a process for preparing isotacticpolyolefins by polymerization of at least one α-olefin, in particularpropylene in the presence of a catalyst system prepared by the processjust mentioned.

The invention further provides the polyolefins obtainable by one of theabovementioned polymerization processes, in particular homopolymers andcopolymers of propylene, and also provides polyolefin compositions whichcomprise polyolefins obtainable using the catalyst systems of thepresent invention.

The isotactic polypropylenes which can be prepared by the process of thepresent invention have a viscosity number (or index of viscosity, I.V.)greater than 1, a melting point (T_(m)) greater than 158° C., preferablygreater than 160° C., in particular greater than 163° C., anisotacticity determined by pentad analysis of the ¹³C-NMR spectrum ofthe polymer samples of greater than 98%, in particular greater than 99%,a frequency of reverse insertions determined by pentad analysis of the¹³C-NMR spectrum of the polymer samples of less than 0.3%, in particularless than 0.25%, and a polydispersity Q=Mw/Mn of less than 3, inparticular less than 2.5.

The polymers prepared by the process of the present invention andpolyolefin compositions in which they are present are particularlyuseful for producing films, fibers and moldings.

The invention further provides films, fibers and moldings produced fromthe above-described polyolefin compositions.

The invention is illustrated by the following nonlimiting examples.

EXAMPLES

General Procedures

Synthesis and handling of the organic metal compounds and the catalystswere carried out in the absence of air and moisture under argon (Glovebox and Schlenk technique). All solvents used were purged with argon anddried over molecular sieves before use.

(S,S)-(+)-N,N′-bis(3,5-di-tert-butylsalicylidene)-1,2-diaminocyclohexane,(R,R)-(−)-N,N′-bis(3,5-di-tert-butylsalicylidene)-1,2-diaminocyclohexaneand(S,S)-(+)N,N′-bis(3,5-di-tert-butylsalicylidene)-1,2-diaminocyclohexanechromium(III)chloridewere commercially available. The preparation of supported catalystsystems was carried out using a silica of the type XPO 2107 from Gracedried at 180° C. under reduced pressure for is hours as silica gel.

Determination of the Melting Point:

The melting point T_(m) was determined by means of a DSC measurement inaccordance with ISO standard 3146 using a first heating phase at aheating rate of 20° C. per minute to 200° C., a dynamic crystallizationat a cooling rate of 20° C. per minute down to 25° C. and a secondheating phase at a heating rate of 20° C. per minute back to 200° C. Themelting point was then the temperature at which the curve of enthalpyversus temperature measured in the second heating phase displayed itsmaximum.

Gel Permeation Chromatography:

Gel permeation chromatography (GPC) was carried out at 145° C. in1,2,4-trichlorobenzene using a Waters 150C GPC apparatus The data wereevaluated using the software Win-GPC from HS-Entwicklungsgesellschaftfür wissenschaftliche Hard-und Software mbH. Oberhilbersheim. Thecolumns were calibrated by means of polypropylene standards having molarmasses ranging from 100 to 10⁷ g/mol. Mass average molar masses (M_(w))and number average molar masses (M_(n)) of the polymers were determined.The Cl value is the ratio of mass average (M_(w)) to number average(M_(n)).

Determination of the Viscosity Number (I.V.):

The viscosity number was determined in an Ubbelohde viscometer PVS 1provided with an S 5 measuring head (both from Lauda) in decalin at 135°C. For the sample preparation, 20 mg of polymer were dissolved in 20 mlof decalin at 135° C. over a period of 2 hours. 15 ml of the solutionwere introduced into the viscometer and the instrument carried out aminimum of 3 running-out time measurements until a consistent result wasobtained. From the running-out times, the I.V. was determined via theequation I.V.=(t/t_(o)−1)*1/c. where t: mean of the running-out time ofthe solution, t_(o): mean of the running-out time of the solvent, c:concentration of the solution in g/ml.

Example 1 Synthesis of(S,S)-(+)-N,N′-bis(3,5-di-tert-butylsalicylidene)-1,2-diaminocyclohexane-titanium(IV)dichloride (1)

1.4 ml of a solution of n-butyllithium in hexane (3.6 mmol. 2.5M) wasslowly added at room temperature to a solution of 1 g (1.8 mmol) of(S,S)-(+)-N,N′-bis(3,5-di-tert-butylsalicylidene)-1,2-diaminocyclohexanein 70 ml of diethyl ether. The yellow solution was stirred at roomtemperature for 1.5 hours and subsequently admixed with 0.34 g (1.8mmol) of TiCl₄. The reaction mixture was stirred at room temperature for18 hours, subsequently filtered and the solvent was removed in an oilpump vacuum. This gave 0.85 g of (1) as a red, free-flowing powder.

Example 2 Synthesis of(S,S-(+)-N,N′-bis(3,5-di-tert-butylsalicylidene)-1,2-diaminocyclohexanezirconium(IV)dichloride (2)

6.8 ml of a solution of n-butyllithium in hexane (10.9 mmol, 1.6M inhexane) were slowly added at room temperature to a solution of 2.94 g(5.38 mmol) of(S,S)-(+)-N,N′-bis-(3,5-di-tert-butylsalicylidene)-1,2-diaminocyclohexanein 100 ml of diethyl ether and the reaction mixture was stirred for 4hours. 1.24 g (5-34 mmol) of ZrCl₄ were subsequently added a little at atime and the reaction mixture was stirred overnight. The solvents weresubsequently removed in an oil pump vacuum, the solid was taken up indichloromethane, filtered and dichloromethane was removed from thefiltrate in an oil pump vacuum. This gave 4.06 g of (2) as a brightyellow, free-flowing powder.

Example 3 Synthesis of(R,R)-(−)-N,N′-bis(3,5-di-tert-butylsalicylidene)-1,2-diaminocyclohexanezirconium(IV)dichloride (3)

Using a method analogous to example 2, a solution of 3.3 g (6.04 mmol)of(R,R)-(−)-N,N′-bis(3,5-di-tert-butylsalicylidene)-1,2-diaminocyclohexanein 100 ml of diethyl ether was reacted with 7.55 ml of a solution ofn-butyllithium in hexane (12.08 mmol, 1.6M). 1.4 g (6.04 mmol) of ZrCl₄were subsequently added. Work-up by a method analogous to example 2 gave4.77 g of (3) as a bright yellow, free-flowing powder. Crystals wereobtained from a saturated solution of (3) in methylene chloride.

X-ray crystal structure analysis: FIGS. 1 a and 1 b show the structureof the compound (3) from different perspectives.

Example 4 Homopolymerization of Propene

4 ml of a solution of triisobutyl aluminum in hexane (4 mmol, 1M) wereplaced in a 1l reactor. 250 g of propylene were introduced at 30° C. andthe contents of the reactor were heated to 50° C. A catalyst solutionprepared by combining 10 mg of the titanium compound (1) (15.1 μmol)from example 1 with 2.5 ml of a solution of methylaluminoxane in toluene(3.95 mmol, 10% by weight) and subsequently allowing the mixture toreact for 15 minutes was introduced into the reactor together with 50 gof propylene which had a temperature of 80° C. The contents of thereactor were stirred at 50° C. for 0.5 hour and the polymerizationreaction was stopped by venting the reactor. 5 ml of methanol were addedto the contents of the reactor. The polymer was dried overnight underreduced pressure, giving 2.00 g of polypropylene. The results of thepolymerization and the results of the polymer analysis are shown intable 1 below.

Example 5 Homopolymerization of Propene

The polymerization was carried out in a manner analogous to example 4. 4ml of a solution of triisobutylaluminum in hexane (4 mmol, 1M) togetherwith 250 g of propylene were placed in the reactor at 30° C. and themixture was heated to 50° C. A catalyst solution prepared by combining10 mg of the zirconium compound (2) (14.1 μmol) from example 2 with 2.5ml of a solution of methylaluminoxane in toluene (3.95 mmol, 10% byweight) and subsequently allowing the mixture to react for 15 minuteswas introduced into the reactor together with 50 g of propylene whichwas at a temperature of 80° C. The contents of the reactor were stirredat 50° C. for 0.5 hour. After completion of the reaction and work-up ofthe polymer, 3.30 g of polypropylene were obtained. The results of thepolymerization and the results of the polymer analysis are shown intable 1 below. FIG. 2 shows the ¹³C-NMR spectrum of the polymer.Analysis of the ¹³C-NMR spectrum indicated a content of mmmm pentads of99.2%. Reverse insertions could not be detected.

Example 6 Homopolymerization of Propane (Corresponds to 00022-176)

The polymerization was carried out in a manner analogous to example 4. 4ml of a solution of triisobutyl aluminum in hexane (4 mmol, 1M) and 5 mlof MAO (7.9 mmol, 10% by weight) together with 250 g of propylene wereplaced in the reactor at 30° C., 50 ml of hydrogen were added and themixture was heated to 50° C. A catalyst solution prepared by combining20 mg of the zirconium compound (2) (28.3 μmol) from example 2 with 3.9ml of a solution of methylaluminoxane in toluene (6.2 mmol, 10% byweight) and subsequently allowing the mixture to react for 15 minuteswas introduced into the reactor together with 50 g of propylene whichhad a temperature of 80° C. The reactor was heated to 70° C. and thecontents of the reactor were stirred at 70° C. for 0.5 hour. Aftercompletion of the reaction and work-up of the polymer, 18 g ofpolypropylene were obtained. The results of the polymerization and theresults of the polymer analysis are shown in table 1 below,

Example 7 Homopolymerization of Propene

The polymerization was carried out in a manner analogous to example 6. 4ml of a solution of triisobutylaluminum in hexane (4 mmol, 1M) end 5 mlof MAO (7.9 mmol, 100% by weight) together with 250 g of propylene wereplaced in the reactor at 30° C., 50 ml of hydrogen were added and themixture was heated to 50° C. A catalyst solution prepared by combining10 mg of the zirconium compound (2) (14.1 μmol) from example 2 with 3.9ml of a solution of methylaluminoxane in toluene (6.2 mmol, 10% byweight) and subsequently allowing the mixture to react for 15 minuteswas introduced into the reactor together with 50 g of propylene whichhad a temperature of 80° C. The reactor was heated to 70° C. and thecontents of the reactor were stirred at 70° C. for 0.5 hour. Aftercompletion of the reaction and work-up of the polymer, 26 g ofpolypropylene were obtained. The results of the polymerization and theresults of the polymer analysis are shown in table 1 below.

Example 8 Homopolymerization of Propene

The polymerization was carried out in a manner analogous to example 4. 4ml of a solution of triisobutylaluminum in hexane (4 mmol, 1M) togetherwith 250 g of propylene were placed in the reactor at 30° C. and themixture was heated to 50° C. A catalyst solution prepared by combining10 mg of(S,S)-(+)-N,N′-bis(3,5-di-tert-butylsalicylidene)-1,2-diaminocyclohexanechromium(III)chloride (15.8 μmol) with 3.3 ml of a solution of methylaluminoxane intoluene (15.8 mmol, 30% by weight) and subsequently allowing the matureto react for 15 minutes was introduced into the reactor together with 50g of propylene which was at a temperature of 80° C. The contents of thereactor were stirred at 70° C. for 1.0 hour. After completion of thereaction and work-up of the polymer, 0.15 g of polypropylene wasobtained. The results of the polymerization and the results of thepolymer analysis are shown in table 1 below.

Example 9 Copolymerization of Propene with Ethylene

The polymerization was carried out in a manner analogous to example 8. 4ml of a solution of triisobutylaluminum in hexane (4 mmol, 1M) togetherwith 250 g of propylene were placed in the reactor at 30° C. and themixture was heated to 50° C. A catalyst solution prepared by combining10 mg of(S,S)-(+)-N,N′-bis(3,5-di-tert-butylsalicylidene)-1,2-diaminocyclohexanechromium(III)chloride (15.8 μmol) with 3.3 ml of a solution of methylaluminoxane intoluene (15.8 mmol, 30% by weight) and subsequently allowing the mixtureto react for 15 minutes was introduced into the reactor together with 50g of propylene which was at a temperature of 80° C. The contents of thereactor were heated to 70° C., ethylene was introduced into the reactorat a gauge pressure of 2 bar and the mixture was stirred at 70° C. for1.0 hour. After completion of the reaction and work-up of the polymer,1.9 g of polymer were obtained. The results of the polymerization areshown in table 1 below.

Example 10 Homopolymerization of Propene

The polymerization was carried out in a manner analogous to example 8. 4ml of a solution of triisobutylaluminum in hexane (4 mmol, 1M) togetherwith 250 g of propylene were placed in the reactor at 30° C. 100 ml ofhydrogen were added and the mixture was heated to 50° C. A catalystsolution prepared by combining 5 mg of(S,S)-(+)-N,N′-bis(3,5-di-tert-butylsalicylidene)-1,2-diaminocyclohexanechromium(III)chloride (15.8 μmol) and 3.3 ml of a solution of methyl aluminoxane intoluene (15.8 mmol, 30% by weight) and subsequently allowing the mixtureto react for 15 minutes was introduced into the reactor together with 50g of propylene which was at a temperature of 80° C. The contents of thereactor were stirred at 70° C. for 0.5 hour. After completion of thereaction and work-up of the polymer, 4.8 g of polypropylene wereobtained. The results of the polymerization are shown in table 1 below.TABLE 1 Al/TM Activity Melting point Viscosity M_(w) Example TM[mol/mol] [kg/(g * h)] [° C.] No. [dl/g] [kg/mol] Q 4 Ti 262 0.4 158.31.8 502 6.1 5 Zr 280 0.66 166.3 4.4 1050 3.0 6 Zr 500 1.8 165 1.9 2432.1 7 Zr 1000 5.2 163 1.5 8 Cr 1000 0.2 163.5 9 Cr 1000 0.2 10 Cr 21001.92 12 Zr 3030 15.4 160 2.6 297 2.0Units and abbreviations: Al/TM is the molar ratio of the amount ofaluminum from the MAO to the amount of the transition metal complex;activity in kg_(polymer)/(g_(transition metal compound) *h_(polymerization time)); weight average molar mass determined by GPC;polydispersity Q = Mn/Mw.

Example 11 Application of(S,S)-(+)-N,N′-bis(3,5-di-tert-butylsalicylidene)-1,2-diaminocyclohexanezirconium(IV)dichloride to a support

1 g of silica gel was suspended in 15 ml of toluene. 70.3 mg of(S,S)-(+)-N,N′-bis(3,5-di-tert-butylsalicylidene)-1,2-diaminocyclohexanezirconium(IV)dichloride (2) (0.1 mmol) were added and the mixture was refluxed for 2hours. A yellow powder was formed; the supernatant solution wascolorless. Toluene was removed and the powder was dried in an oil pumpvacuum for 2 hours. This gave 1.1 g of yellow powder.

Example 12 Homopolymerization of Propene

The polymerization was carried out in a manner analogous to example 4. 4ml of a solution of triisobutylaluminum in hexane (4 mmol, 1M) togetherwith 250 g of propylene were placed in the reactor at 30° C. and thecontents of the reactor were heated to 50° C. At 50° C., 50 ml ofhydrogen were added. 8.4 ml of a 30% strength solution ofmethylaluminoxane in toluene (40 mmol) were then injected and 0.402 g ofthe powder prepared in example 11 suspended in 2 ml of hexane weresubsequently introduced into the reactor together with 50 g of propylenewhich had a temperature of 80° C. The reactor was heated to 70° C. andthe contents of the reactor were stirred at 70° C. for 0.5 hour. Aftercompletion of the reaction and work-up of the polymer, 8.4 g ofpolypropylene having a melting point of 162.1° C. were obtained.

Example 13 Application of(S,S-(+)-N,N′-bis(3.5-di-tert-butylsalicylidene)-1,2-diaminocyclohexanezirconium(IV)dichloride to a support

2 g of silica gel were suspended in 10 ml of toluene at room temperatureand 5.2 ml of 30% strength MAO solution in toluene were slowly addeddropwise. The mixture was stirred for 2 hours, filtered and the residuewas dried in an oil pump vacuum for 1 hour. 56.7 mg (0.08 mmol) of(S,S)-(+)-N,N′-bis(3,5-di-tert-butylsalicylidene)-1,2-diaminocyclohexanezirconium(IV)dichloride (2) were dissolved in 8 ml of toluene, admixed with 0.9 ml of30% strength MAO solution in toluene and the mixture was stirred for 1hour. The silica gel which had been treated with MAO was dried,suspended in 10 ml of toluene and the solution of zirconium complex/MAOwas slowly added dropwise. After stirring for 1 hour, toluene wasremoved and the solid was dried in an oil pump vacuum. This gave 3.19 gof a yellow, free-flowing powder.

Example 14 Homopolymerization of Propene

The polymerization was carried out in a manner analogous to example 4. 4ml of a solution of triisobutylaluminum in hexane (4 mmol, 1M) togetherwith 250 g of propylene were placed in the reactor at 30° C. and thecontents of the reactor were heated to 50° C. At 50° C., 50 ml ofhydrogen were added. 2.288 g of the powder prepared in example 13suspended in hexane were then introduced into the reactor together with50 g of propylene which was at a temperature of 80° C. The reactor washeated to 70° C. and the contents of the reactor were stirred at 70° C.for 0.5 hour. After completion of the reaction and work-up of thepolymer, 4.3 g of polypropylene having a melting point of 151.1° C. wereobtained.

1. A catalyst system for preparing isotactic polyolefins obtainable by reacting at least one chiral transition metal compound and at least one cocatalyst which is able to convert the chiral transition metal compound into a cation, where the chiral transition metal compound consists of two bidentate chelating ligands connected to one another via a bridge and, optionally one or two further monodentate ligands, with the four coordinating atoms of the two chelating ligands being in an approximately planar arrangement around the transition metal ion and up to two further ligands being located above and below this approximately planar coordination sphere formed by the four coordinating atoms of the two chelating ligands and, in the case of two such further ligands, these being in the trans position relative to one another.
 2. A catalyst system as claimed in claim 1, wherein the chiral transition metal compound is a transition metal compound of the formula (I) or one of its enantiomers of the formula (I*),

where M is an element of group 3, 4, 5, 6, 7, 8, 9, 10, 11 or 12 of the Periodic Table of the Elements or the lanthanides, z are identical or different and are each an organic or inorganic anionic ligand, n1 and n2 are identical or different and are each 0 or 1, where n1+n2+2 corresponds to the valence of M, R¹ and R² are identical or different and are each a C₁-C₄₀ radical, or R¹ and R² together with the atoms connecting them form a cyclic or polycyclic ring system which may contain one or more, identical or different heteroatoms selected from the group consisting of the elements N, O, P, S and Si in place of carbon atoms in the ring system, R³ is hydrogen or a C₁-C₄₀ radical, where R³ displays lower steric hindrance than R¹, R⁴ is hydrogen or a C₁-C₄₀ radical, where R⁴ displays lower steric hindrance than R², R⁵ and R⁶ are identical or different and are each hydrogen or a C₁-C₄₀ radical, or R¹ and R³, R² and R⁴, R¹ and R⁵ and/or R² and R⁶ together with the atoms connecting them in each case form a cyclic or polycyclic ring system which may contain one or more, identical or different heteroatoms selected from the group consisting of the elements N, O, P, S and Si in place of carbon atoms in the ring system, X is a single bond between the two carbon atoms or is a divalent group, Y¹ and Y² are identical or different and are each oxygen, sulfur, selenium, tellurium, an NR⁹ group or a PR⁹ group, R⁷ R⁸ and R⁹ are identical or different and are each hydrogen, C₁-C₂₀-alkyl, C₂-C₂₀-alkenyl, C₆-C₂₂-aryl, alkylaryl or arylalkyl having from 1 to 10 carbon atoms in the alkyl part and from 6 to 22 carbon atoms in the aryl part, T¹ T², T³ and T⁴ are identical or different and are each hydrogen or a C₁-C₄₀ radical, or T¹ and T³ and/or T² and T⁴ together with the carbon atoms connecting them in each case form a cyclic or polycyclic ring system which may contain one or more, identical or different heteroatoms selected from the group consisting of the elements N, O, P, S and Si in place of carbon atoms in the ring system.
 3. A catalyst system as claimed in claim 2, wherein the chiral transition metal compound of the formula (I) or (I*) is a transition metal compound of the formula (Ia) or one of its enantiomers of the formula (Ia*),

where M is an element of group 4 or 6 of the Periodic Table of the Elements, Z are identical or different and are each halogen, hydrogen, C₁-C₁₀-alkyl, C₆-C₁₄-aryl, alkylaryl or arylalkyl having from 1 to 4 carbon atoms in the alkyl part and from 6 to 10 carbon atoms in the aryl part, n1 and n2 are identical or different and are each 0 or 1, with n1+n2+2 corresponding to the valence of M, R¹ and R² are identical or different and are each a C₁-C₄₀ radical, or R¹ and R² together with the atoms connecting them form a cyclic or polycyclic ring system which may contain one or more, identical or different heteroatoms selected from the group consisting of the elements N, O, P, S and Si in place of carbon atoms in the ring system, R⁵ and R⁶ are identical and are each hydrogen or a C₁-C₄₀ radical, R¹⁰, R¹¹, R¹² and R¹³ are identical or different and are each hydrogen or a C₁-C₄₀ radical, or two adjacent radicals R¹⁰, R¹¹, R¹² and R¹³ together with the two connecting carbon atoms may form a cyclic ring system.
 4. A catalyst system as claimed claim 1, wherein the cocatalyst is an aluminoxane.
 5. A catalyst system as claimed in claim 1, which further comprises a support.
 6. (canceled)
 7. A process for preparing polyolefins by polymerization or copolymerization of at least one olefin in the presence of a catalyst system as claimed in claim
 1. 8. A chiral transition metal compound of the formula (Ib) or one of its enantiomers of the formula (Ib*)

where M is an element of group 3, 4, 5, 6, 7, 8, 9, 10, 11 or 12 of the Periodic Table of the Elements or the lanthanides, Z are identical or different and are each an organic or inorganic anionic ligand, n1 and n2 are identical or different and are each 0 or 1, where n1+n2+2 corresponds to the valence of M, R¹ and R² are identical or different and are each a C₁-C₄₀ radical, or R¹ and R²together with the atoms connecting them form a cyclic or polycyclic ring system which may contain one or more, identical or different heteroatoms selected from the group consisting of the elements N, O, P, S and Si in place of carbon atoms in the ring system, R³ is hydrogen or a C₁-C₄₀ radical, where R³ displays lower steric hindrance than R¹, R⁴ is hydrogen or a C₁-C₄₀ radical, where R⁴ displays lower steric hindrance than R², R⁵ and R⁶ are identical or different and are each hydrogen or a C₁-C₄₀ radical, or R¹ and R³, R² and R⁴, R¹ and R⁵ and/or R² and R⁶ together with the atoms connecting them in each case form a cyclic or polycyclic ring system which may contain one or more, identical or different heteroatoms selected from the group consisting of the elements N, O, P, S and Si in place of carbon atoms in the ring system, X is a single bond between the two carbon atoms or is a divalent group, Y¹ and Y² are identical or different and are each oxygen, sulfur, selenium, tellurium, an NR⁹ group or a PR⁹ group, R⁷, R⁸ and R⁹ are identical or different and-are each hydrogen, C₁-C₂₀-alkyl, C₂-C₂₀-alkenyl, C₆-C₂₂-aryl, alkylaryl or arylalkyl having from 1 to 10 carbon atoms in the alkyl part and from 6 to 22 carbon atoms in the aryl part, T¹ T², T³ and T⁴ are identical or different and are each hydrogen or a C₁-C₄₀ radical, or T¹ and T³ and/or T² and T⁴ together with the carbon atoms connecting them in each case form a cyclic or polycyclic ring system which may contain one or more, identical or different heteroatoms selected from the group consisting of the elements N, O, P, S and Si in place of carbon atoms in the ring system.
 9. A chiral transition metal compound of the formula (Ib) or (Ib*) as claimed in claim 8, wherein M is zirconium or hafnium.
 10. A process for preparing a catalyst system for olefin polymerization, which comprises reacting at least one transition metal compound of the formula (Ib) or (Ib*) as claimed in claim 8 with at least one cation-forming compound.
 11. A process for preparing isotactic polyolefins by polymerization of at least one a-olefin in the presence of a catalyst system prepared by a process as claimed in claim
 10. 12-14. (canceled) 